**Triangles, squares, rectangles, pentagons, hexagons and octagons are some of the most common polygons.** A polygon is a plane figure with many sides made up of line segments.

Polygons are named according to the number of sides they have. Triangles have three sides, quadrilaterals have four sides, and pentagons have five sides. Polygons with more than six sides are often called "n-gons," where n represents the number of sides the polygon has. A polygon with 15 sides, for example, would be called a 15-gon.

There are many examples of polygons in the world. Honeycombs are made up of many different hexagons, or six-sided shapes. Stop signs are one of the most-recognizable examples of an octagon. A mirror with four right angles and four equal sides is a square, which is a type of quadrilateral. The Pentagon building in Washington, D.C. got its name because it has five sides. Ceiling tiles come in several different shapes, from basic squares to intricate octagons.

Polygons are further classified as concave or convex. A concave polygon has what is known as a reflex angle. A reflex angle measures more than 180 degrees. Polygons without reflex angles are convex polygons. Triangles, quadrilaterals and pentagons are examples of convex polygons.